Allow updating gopass.exe on Windows

Windows will lock files being executed but we should be able to rename
them.

Fixes #2011

RELEASE_NOTES=[BUGFIX] Fix updater on Windows.

Signed-off-by: Dominik Schulz <dominik.schulz@gauner.org>

internal/action/update.go

@@ -1,9 +1,6 @@
 package action
 
 import (
-	"fmt"
-	"runtime"
-
 	"github.com/gopasspw/gopass/internal/action/exit"
 	"github.com/gopasspw/gopass/internal/out"
 	"github.com/gopasspw/gopass/internal/updater"
@@ -23,10 +20,6 @@ func (s *Action) Update(c *cli.Context) error {
 		return nil
 	}
 
-	if runtime.GOOS == "windows" {
-		return fmt.Errorf("gopass update is not supported on windows (#1722)")
-	}
-
 	out.Printf(ctx, "⚒ Checking for available updates ...")
 	if err := updater.Update(ctx, s.version); err != nil {
 		return exit.Error(exit.Unknown, err, "Failed to update gopass: %s", err)

internal/updater/access_others.go

@@ -8,3 +8,8 @@ import "golang.org/x/sys/unix"
 func canWrite(path string) error {
 	return unix.Access(path, unix.W_OK) //nolint:wrapcheck
 }
+
+func removeOldBinary(dir, dest string) error {
+	// no need, os.Rename will replace the destination
+	return nil
+}

internal/updater/access_windows.go

@@ -6,3 +6,24 @@ package updater
 func canWrite(path string) error {
 	return nil
 }
+
+// Windows won't allow us to remove the binary that's currently being executed.
+// So rename the binary and then the updater should be able to write it's
+// update to the correct location.
+//
+// See https://stackoverflow.com/a/459860
+func removeOldBinary(dir, dest string) error {
+	bakFile := filepath.Join(dir, filepath.Base(dest)+".bak")
+	// check if the bakup file already exists
+	if _, err := os.Stat(bakFile); err == nil {
+		// ... then remove it
+		_ = os.Remove(bakFile)
+	}
+	// we can't remove the currently running binary, but should be able to
+	// rename it.
+	if err := os.Rename(dest, bakFile); err != nil {
+		return fmt.Errorf("unable to rename %s to %s: %w", dest, bakFile, err)
+	}
+
+	return nil
+}

internal/updater/extract.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -17,26 +18,40 @@ import (
 
 func extractFile(buf []byte, filename, dest string) error {
 	mode := os.FileMode(0o755)
+	dir := filepath.Dir(dest)
 
 	// if overwriting an existing binary retain it's mode flags
 	fi, err := os.Lstat(dest)
 	if err == nil {
 		mode = fi.Mode()
 	}
 
-	if err := os.Remove(dest); err != nil {
-		if !os.IsNotExist(err) {
-			return fmt.Errorf("unable to remove destination file: %w", err)
-		}
+	tfn, err := extractToTempFile(buf, filename, dest)
+	if err != nil {
+		return fmt.Errorf("failed to extract update to %s: %w", dest, err)
+	}
+
+	if err := removeOldBinary(dir, dest); err != nil {
+		return fmt.Errorf("failed to remove old binary %s: %w", dest, err)
 	}
 
-	// open the destination file for writing
-	dfh, err := os.OpenFile(dest, os.O_WRONLY|os.O_CREATE|os.O_EXCL, mode)
+	if err := os.Rename(tfn, dest); err != nil {
+		return fmt.Errorf("failed to rename tempfile %s to %s: %w", tfn, dest, err)
+	}
+
+	return os.Chmod(dest, mode)
+}
+
+func extractToTempFile(buf []byte, filename, dest string) (string, error) {
+	// open a temp file for writing
+	dir := filepath.Dir(dest)
+	dfh, err := ioutil.TempFile(dir, "gopass")
 	if err != nil {
-		return fmt.Errorf("failed to open file %q: %w", dest, err)
+		return "", fmt.Errorf("failed to create temp file in %s: %w", dir, err)
 	}
 
 	defer func() {
+		_ = dfh.Sync()
 		_ = dfh.Close()
 	}()
 
@@ -46,23 +61,23 @@ func extractFile(buf []byte, filename, dest string) error {
 	case ".gz":
 		gzr, err := gzip.NewReader(rd)
 		if err != nil {
-			return fmt.Errorf("failed to open gzip file: %w", err)
+			return "", fmt.Errorf("failed to open gzip file: %w", err)
 		}
 
-		return extractTar(gzr, dfh, dest)
+		return extractTar(gzr, dfh, dfh.Name())
 	case ".bz2":
-		return extractTar(bzip2.NewReader(rd), dfh, dest)
+		return extractTar(bzip2.NewReader(rd), dfh, dfh.Name())
 	case ".zip":
-		return extractZip(buf, dfh, dest)
+		return extractZip(buf, dfh, dfh.Name())
 	default:
-		return fmt.Errorf("unsupported file extension: %q", filepath.Ext(filename))
+		return "", fmt.Errorf("unsupported file extension: %q", filepath.Ext(filename))
 	}
 }
 
-func extractZip(buf []byte, dfh io.WriteCloser, dest string) error {
+func extractZip(buf []byte, dfh io.WriteCloser, dest string) (string, error) {
 	zrd, err := zip.NewReader(bytes.NewReader(buf), int64(len(buf)))
 	if err != nil {
-		return fmt.Errorf("failed to open zip file: %w", err)
+		return "", fmt.Errorf("failed to open zip file: %w", err)
 	}
 
 	for i := 0; i < len(zrd.File); i++ {
@@ -72,26 +87,26 @@ func extractZip(buf []byte, dfh io.WriteCloser, dest string) error {
 
 		file, err := zrd.File[i].Open()
 		if err != nil {
-			return fmt.Errorf("failed to read from zip file: %w", err)
+			return "", fmt.Errorf("failed to read from zip file: %w", err)
 		}
 
 		n, err := io.Copy(dfh, file)
 		if err != nil {
 			_ = dfh.Close()
 			_ = os.Remove(dest)
 
-			return fmt.Errorf("failed to read gopass.exe from zip file: %w", err)
+			return "", fmt.Errorf("failed to read gopass.exe from zip file: %w", err)
 		}
 		// success
 		debug.Log("wrote %d bytes to %v", n, dest)
 
-		return nil
+		return dest, nil
 	}
 
-	return fmt.Errorf("file not found in archive")
+	return "", fmt.Errorf("file not found in archive")
 }
 
-func extractTar(rd io.Reader, dfh io.WriteCloser, dest string) error {
+func extractTar(rd io.Reader, dfh io.WriteCloser, dest string) (string, error) {
 	tarReader := tar.NewReader(rd)
 
 	for {
@@ -101,7 +116,7 @@ func extractTar(rd io.Reader, dfh io.WriteCloser, dest string) error {
 		}
 
 		if err != nil {
-			return fmt.Errorf("failed to read from tar file: %w", err)
+			return "", fmt.Errorf("failed to read from tar file: %w", err)
 		}
 
 		name := filepath.Base(header.Name)
@@ -119,13 +134,13 @@ func extractTar(rd io.Reader, dfh io.WriteCloser, dest string) error {
 			_ = dfh.Close()
 			_ = os.Remove(dest)
 
-			return fmt.Errorf("failed to read gopass from tar file: %w", err)
+			return "", fmt.Errorf("failed to read gopass from tar file: %w", err)
 		}
 		// success
 		debug.Log("wrote %d bytes to %v", n, dest)
 
-		return nil
+		return dest, nil
 	}
 
-	return fmt.Errorf("file not found in archive")
+	return "", fmt.Errorf("file not found in archive")
 }